If I plan one or more conditional moves, is it possible for my opponent to see which moves I have planned? I hope not, because it might give my opponent a hint towards the best move in that position. I could not find the answer to this question in this forum, so excuse me if it is already mentionned somewhere.

Just for the sake of complete clarity since you asked - though not directly related - notes written to Malkovich log can however be viewed by your opponent under some circumstances. Malkovich log does not serve as private notes.

I have been thinking about starting to use the Malkovich log, but I noticed that it is available to be viewed by everyone except your opponent (when your opponent is logged in.) I would much rather have the Malkovich log be private (visible only to me) until the game is complete.
I’m just wondering if there are any compelling arguments to leave it visible to everyone during the game.